The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
When an image of a fixed area is continuously inputted, such as to a closed-circuit television (CCTV) or the like, and when an abnormality has occurred in a camera, a technique to analyze the abnormality is required. A known image determining apparatus receives an image and generates an input edge image of an object appearing on the image by obtaining a gradient of the image. Thereafter, the image determining apparatus determines a similarity value of the input edge image to a reference edge image that is an accumulated image with a fixed edge. When the similarity value is less than a predetermined value, the image determining apparatus generates a tampering mark. When this tampering mark is generated on a predetermined number of consecutive images, it is determined that a tampering has occurred. When there is no tampering, the reference edge image is updated, thus determining whether or not a camera tampering has occurred.
The tampering means a state in which a normal image input is hampered due to an abnormality of a camera. In other words, the tampering includes not only a trouble of the device itself such as a damage on a lens of the camera but also an inability to input an image in a set area due to a directional change of the camera or an obstacle placed in front of the lens.